We propose to further test the delay-reduction hypothesis of conditioned reinforcement in more complex procedures involving choice and observing; in assessing the extent to which a new extension of the delay-reduction hypothesis may account for elicited and discriminative responding in the presence of a stimulus and in describing choice for aversive schedules; in developing a new choice paradigm in which choice responses produce food as well as situation transitions, in part to test under what conditions choice will be sensitive to relatively long-term consequences; in entering relatively new areas--for this laboratory--namely the study of response topography in pigeons and feeding behavior in rats. Proposed experiments seek to accomplish several additional goals including: (1) assessing the determinants of respondent and operant behavior; (2) testing the conditions under which Luce's constant-ratio rule of choice is upheld; (3) further assessing conditions in which choice will exhibit transitivity; (4) continuing our investigation of the symmetry of reward and punishment, including devising a better procedure for studying schedules of aversive control and conducting two experiments testing aspects of Herrnstein and Hineline's shock-frequency reduction theory; (5) testing the uncertainty-reduction hypothesis of observing with human subjects. Finally, at least some of the experiments in each of the five major sections of the proposal should further our understanding of behavior on chain schedules and behavior maintained by conditioned reinforcement.